Frequency splitting, nematics

In an aligned nematic with Axm > 0, the angle between the magnetic field and n, is zero and, for a molecule assumed to have cylindrical symmetry (i.e. we ignore any molecular biaxiality, Skk - Smm = 0), the separation in frequency between the two transitions in Eq. (5.12), Av = v+ — v (the quadrupolar splitting), is given... 

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